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Income Taxes - Schedule of Effective Income Tax Rate (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Tax Disclosure [Abstract]      
Income Taxes at Federal Statutory Rate $ 77,047 $ 76,332 $ 75,082
Increases (Decreases) in Tax from:      
State Taxes on Income, Net of Federal Tax 14,360 14,429 15,049
Production Tax Credits (PTCs) (20,106) (17,394) (14,985)
Amortization of Excess Deferred Income Taxes (2,788) (2,205) (1,625)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax (586) (586) (586)
Other, Net (2,697) (1,278) 416
Income Taxes at Effective Tax Rate $ 65,230 $ 69,298 $ 73,351
Income Taxes at Federal Statutory Rate 21.00% 21.00% 21.00%
Increases (Decreases) in Tax from:      
State Taxes on Income, Net of Federal Tax 3.90% 4.00% 4.20%
Production Tax Credits (PTCs) (5.50%) (4.80%) (4.20%)
Amortization of Excess Deferred Income Taxes (0.80%) (0.60%) (0.50%)
North Dakota Wind Tax Credit Amortization, Net of Federal Tax (0.20%) (0.20%) (0.20%)
Other, Net (0.60%) (0.30%) 0.20%
Income Taxes at Effective Tax Rate 17.80% 19.10% 20.50%